Blood supply of the lung diagram. Lungs

Table of contents for the topic "Respiratory system (systema respiratorium).":

Circulation in the lungs. Blood supply to the lungs. Lung innervation. Vessels and nerves of the lungs.

In connection with the function of gas exchange, the lungs receive not only arterial, but also venous blood. The latter flows through the branches of the pulmonary artery, each of which enters the gate of the corresponding lung and then divides according to the branching of the bronchi. The smallest branches of the pulmonary artery form a network of capillaries braiding the alveoli (respiratory capillaries). Venous blood flowing to the pulmonary capillaries through the branches of the pulmonary artery enters into an osmotic exchange (gas exchange) with the air contained in the alveoli: it releases its carbon dioxide into the alveoli and receives oxygen in return. The capillaries form veins that carry blood enriched with oxygen (arterial) and then form larger venous trunks. The latter merge further into vv. pulmonales.

A arterial blood delivered to the lungs rr. bronchiales (from the aorta, aa. intercostales posteriores and a. subclavia). They nourish the bronchial wall and lung tissue. From the capillary network, which is formed by the branches of these arteries, are added vv. bronchiales, falling partly into vv. azygos and hemiazygos, and partly in vv. pulmonales. Thus, the systems of the pulmonary and bronchial veins anastomose with each other.

In the lungs, superficial lymphatic vessels are distinguished, laid in the deep layer of the pleura, and deep, intrapulmonary. The roots of deep lymphatic vessels are lymphatic capillaries that form networks around the respiratory and terminal bronchioles, in the interacinus and interlobular septa. These networks continue into the plexuses of the lymphatic vessels around the branches of the pulmonary artery, veins and bronchi.

Draining lymphatic vessels go to the root of the lung and the regional bronchopulmonary and further tracheobronchial and paratracheal lymph nodes lying here, nodi lymphatici bronchopulmonales and tracheobronchiales.

Since the efferent vessels of the tracheobronchial nodes go to the right venous corner, a significant part of the lymph of the left lung, flowing from its lower lobe, enters the right lymphatic duct.

The nerves of the lungs come from plexus pulmonalis, which is formed by branches n. vagus and truncus sympathicus.

Coming out of the named plexus, the pulmonary nerves spread in the lobes, segments and lobules of the lung along the bronchi and blood vessels that make up the vascular-bronchial bundles. In these bundles, the nerves form plexuses, in which microscopic intraorgan nerve knots are found, where preganglionic parasympathetic fibers switch to postganglionic ones.

Three nerve plexuses are distinguished in the bronchi: in the adventitia, in the muscular layer and under the epithelium. The subepithelial plexus reaches the alveoli. In addition to efferent sympathetic and parasympathetic innervation, the lung is supplied with afferent innervation, which is carried out from the bronchi along the vagus nerve, and from the visceral pleura - as part of the sympathetic nerves passing through the cervicothoracic ganglion.

Lung anatomy instructional video

Anatomy of the lungs on the preparation of a corpse from Associate Professor T.P. Khairullina understands

In humans, for the purpose of providing the body with oxygen, there is a whole system - the respiratory system. Its most important component is the lungs. The anatomy of the lungs describes them as a paired organ located in the chest cavity. The name of the organ is due to the fact that when the lung tissue is immersed in water, it does not sink, unlike other organs and tissues. The functions performed, that is, ensuring gas exchange between the environment and the body, leave an imprint on the features of blood flow to the lungs.

The blood supply to the lungs is different in that they receive both arterial and venous blood. The system itself includes:

main vessels.
Arterioles and venules.
capillaries.

Capillaries are divided into two types: narrow (from 6 to 12 microns), wide (from 20 to 40 microns).

An interesting fact regarding the combination of the capillary network and the alveolar walls. Anatomically, it is a single whole, which is called the capillary-alveolar membrane. This fact is decisive in the relationship between the mode of ventilation and blood circulation of the lung.

Arterial blood flow

Arterial blood enters the tissues of the lung from the aorta through the bronchial branches (rr. bronchiales). Normally, the aorta usually “throws out” 2 bronchial branches, one to each lung. Rarely there are more.

Each such vessel branches along with the bronchial tree, braiding the alveoli, supplying blood and nourishing the lung tissue. And their terminal branches are sent:

to the lymphatics.
Esophagus.
Pericardium.
Pleura.

Bronchial vessels enter the system b. circle (large circle). The capillary network of these vessels forms bronchial veins, which partially flow into:

Unpaired and semi-unpaired (vv. azygos, vv. hemiazygos) veins.
And partly in the pulmonary (vv. pulmonales) veins. They are divided into right and left. The number of such veins is from 3 to 5 pieces, less often there are more of them.

This means that the blood supply system of the lung itself has anastomoses (junctions) with a network of vessels designed for gas exchange with the environment or a small circle (m circle).

Venous blood flow

The pulmonary circulation system is provided by the pulmonary vessels (arteries and veins) and their branches. The latter have a diameter of the order of a millimeter.

Elastic.
Able to soften the systolic tremors of the right ventricle of the heart.

The venous "waste" fluid of the body, flowing through the capillaries belonging to the system a. pulmonales and v. pulmonales (pulmonary vessels: arteries and veins), interacts with the osmotic method with the air accumulated in the alveolus, braided by a capillary network. Then small vessels (capillaries) fold into vessels that carry oxygenated blood.

The arteries, on which the pulmonary trunk branches, carry venous blood to the organs of gas exchange. The trunk up to 60 mm long has a diameter of 35 mm, it is divided into 2 branches below the trachea by 20 mm. Having penetrated into the tissues of the lung through its root, these arteries, branching parallel to the bronchi, are divided into:

Segmental.
Equity.

Respiratory bronchioles are accompanied by arterioles. Each such arteriole is wider than its counterparts belonging to a large circle and more elastic than them. This reduces the resistance to blood flow.

The capillaries of this network can be conditionally divided into pre-capillaries and post-capillaries. The latter are combined into venules, enlarged to veins. Unlike the arteries of this circle, such veins are located between the pulmonary lobules, and not parallel to the bronchus.

Branches of veins located inside individual segments of the lungs have unequal diameters and lengths. They flow into intersegmental veins, collecting blood from two adjacent segments.

Interesting features: dependence of blood flow on body position

The structure of the pulmonary system, in terms of organizing its blood supply, is also interesting in that in small and large circles it differs significantly in pressure gradient - a change in pressure per unit path. In the vascular network that provides gas exchange, it is low.

That is, the pressure in the veins (maximum 8 mm Hg) is significantly inferior to it in the arteries. Here it is 3 times more (about 25 mm Hg). The pressure drop per unit path of this circle is on average 15 mm. rt. Art. And this is much less than such a difference in a large circle. This feature of the vascular walls of the small circle is a protective mechanism that prevents pulmonary edema and respiratory failure.

An additional consequence of the described feature is the unequal blood supply in different lobes of the lung in a standing position. It decreases linearly:

Above is less.
In the root part - more intense.

Areas with significantly different blood supply are called Vesta zones. As soon as a person lies down, the difference decreases, and the blood flow becomes more uniform. But at the same time, it increases in the posterior parts of the parenchyma of the organ and decreases in the anterior ones.

1. GENERAL CHARACTERISTICS OF THE RESPIRATORY SYSTEM

1.1. The structure of the respiratory system

Airways (nose, mouth, pharynx, larynx, trachea).
Lungs.
bronchial tree. The bronchus of each lung gives more than 20 consecutive branches. Bronchi - bronchioles - terminal bronchioles - respiratory bronchioles - alveolar passages. The alveolar ducts end in alveoli.
Alveoli. The alveolus is a sac made up of a single layer of thin epithelial cells connected by tight junctions. The inner surface of the alveolus is covered with a layer surfactant(surface-active substance).
The lung is covered on the outside by a visceral pleural membrane. The parietal pleural membrane covers the inside of the chest cavity. The space between the visceral and parietal membranes is called pleural cavity.
Skeletal muscles involved in the act of breathing (diaphragm, internal and external intercostal muscles, muscles of the abdominal wall).

Features of the blood supply to the lungs.

Nourishing blood flow. Arterial blood enters the lung tissue through the bronchial arteries (branches from the aorta). This blood supplies the lung tissue with oxygen and nutrients. After passing through the capillaries, venous blood is collected in the bronchial veins, which flow into the pulmonary vein.
Respiratory blood flow. Venous blood enters the pulmonary capillaries through the pulmonary arteries. In the pulmonary capillaries, the blood is enriched with oxygen and arterial blood enters the left atrium through the pulmonary veins.

1.2. Functions of the respiratory system

The main function of the respiratory system- providing the cells of the body with the necessary amount of oxygen and removing carbon dioxide from the body.

Other functions of the respiratory system:

Excretory - through the lungs, volatile metabolic products are released;
thermoregulatory - breathing promotes heat transfer;
protective - a large number of immune cells are present in the lung tissue.

Breath- the process of gas exchange between cells and the environment.

Stages of respiration in mammals and humans:

Convection transport of air from the atmosphere to the alveoli of the lungs (ventilation).
Diffusion of gases from the air of the alveoli into the blood of the pulmonary capillaries (together with the 1st stage is called external respiration).
Convection transport of gases by blood from lung capillaries to tissue capillaries.
Diffusion of gases from capillaries into tissues (tissue respiration).

1.3. Evolution of the respiratory system

Diffusion transport of gases through the surface of the body (protozoa).
The appearance of a system of convection transfer of gases by blood (hemolymph) to the internal organs, the appearance of respiratory pigments (worms).
The appearance of specialized organs of gas exchange: gills (fish, molluscs, crustaceans), trachea (insects).
The emergence of a system of forced ventilation of the respiratory system (terrestrial vertebrates).

2. MECHANICS OF INHALE AND EXHALE

2.1. respiratory muscles

Ventilation of the lungs is carried out due to periodic changes in the volume of the chest cavity. An increase in the volume of the chest cavity (inhalation) is carried out by contraction inspiratory muscles, decrease in volume (exhalation) - by contraction expiratory muscles.

inspiratory muscles:

external intercostal muscles- contraction of the external intercostal muscles raises the ribs up, the volume of the chest cavity increases.
diaphragm- with the contraction of one's own muscle fibers, the diaphragm flattens and moves downward, increasing the volume of the chest cavity.

expiratory muscles:

internal intercostal muscles- contraction of the internal intercostal muscles lowers the ribs downward, the volume of the chest cavity decreases.
abdominal wall muscles- contraction of the muscles of the abdominal wall leads to a rise in the diaphragm and lowering of the lower ribs, the volume of the chest cavity decreases.

With calm breathing, exhalation is carried out passively - without the participation of muscles, due to the elastic traction of the lungs stretched during inhalation. During forced breathing, expiration is carried out actively - due to the contraction of the expiratory muscles.

Inhale: inspiratory muscles contract - the volume of the chest cavity increases - the parietal membrane stretches - the volume of the pleural cavity increases - the pressure in the pleural cavity falls below atmospheric pressure - the visceral membrane pulls up to the parietal membrane - the volume of the lung increases due to the expansion of the alveoli - the pressure in the alveoli decreases - air from the atmosphere enters lung.

Exhalation: the inspiratory muscles relax, the stretched elastic elements of the lungs contract, (expiratory muscles contract) - the volume of the chest cavity decreases - the parietal membrane contracts - the volume of the pleural cavity decreases - the pressure in the pleural cavity rises above atmospheric pressure - the pressure compresses the visceral membrane - the volume of the lung decreases due to compression of the alveoli - the pressure in the alveoli increases - the air from the lung goes into the atmosphere.

3. VENTILATION

3.1. Volumes and capacities of the lung (for self-preparation)

Questions:

1. Volumes and capacities of the lung

Methods for measuring residual volume and functional residual capacity (helium dilution method, nitrogen washout method).

Literature:

1. Human physiology / In 3 volumes, ed. Schmidt and Thevs. - M., 1996. - v.2., p. 571-574.

Babsky E.B. etc. Human Physiology. M., 1966. - pp. 139-141.
General course of human and animal physiology / Ed. Nozdracheva A.D. - M., 1991. - p. 286-287.

(textbooks are listed in order of suitability for the preparation of the proposed questions)

3.2. Pulmonary ventilation

Pulmonary ventilation is quantified minute volume of breathing(MAUD). MOD - the volume of air (in liters) inhaled or exhaled in 1 minute. Minute respiratory volume (l/min) = tidal volume (l) ´ respiratory rate (min -1). MOD at rest is 5-7 l/min, during exercise MOD can increase up to 120 l/min.

Part of the air goes to the ventilation of the alveoli, and part - to the ventilation of the dead space of the lungs.

anatomical dead space(AMP) is called the volume of the airways of the lungs, because gas exchange does not occur in them. The volume of AMP in an adult is ~150 ml.

Under functional dead space(FMP) understand all those areas of the lungs in which gas exchange does not occur. The volume of the FMF is the sum of the volume of the AMP and the volume of the alveoli, in which gas exchange does not occur. In a healthy person, the volume of FMP exceeds the volume of AMP by 5-10 ml.

Alveolar ventilation(AB) - part of the MOD reaching the alveoli. If the tidal volume is 0.5 L and the FMP is 0.15 L, then AV is 30% MOD.

About 2 from the alveolar air enters the blood, and carbon dioxide from the blood goes into the air of the alveoli. Due to this, the concentration of O 2 in the alveolar air decreases, and the concentration of CO 2 increases. With each breath, 0.5 liters of inhaled air is mixed with 2.5 liters of air remaining in the lungs (functional residual capacity). Due to the entry of a new portion of atmospheric air, the concentration of O 2 in the alveolar air increases, and CO 2 decreases. Thus, the function of pulmonary ventilation is to maintain the constancy of the gas composition of the air in the alveoli.

4. GAS EXCHANGE IN THE LUNGS AND TISSUES

4.1. Partial pressures of respiratory gases in the respiratory system

Dalton's law: the partial pressure (voltage) of each gas in a mixture is proportional to its share of the total volume.
The partial pressure of a gas in a liquid is numerically equal to the partial pressure of the same gas over the liquid under equilibrium conditions.

4.2. Gas exchange in the lungs and tissues

Gas exchange between venous blood and alveolar air is carried out by diffusion. The driving force of diffusion is the difference (gradient) of the partial pressures of gases in the alveolar air and venous blood (60 mm Hg for O 2, 6 mm Hg for CO 2). Diffusion of gases in the lungs is carried out through the aero-hematic barrier, which consists of a layer of surfactant, an alveolar epithelial cell, an interstitial space, and a capillary endothelial cell.

Gas exchange between arterial blood and tissue fluid is carried out in a similar way. (See partial pressures of respiratory gases in arterial blood and tissue fluid).

5. TRANSPORT OF GASES BY BLOOD

5.1. Forms of oxygen transport in the blood

Dissolved in plasma (1.5% O 2)
Associated with hemoglobin (98.5% O 2)

5.2. Binding of oxygen to hemoglobin

The binding of oxygen to hemoglobin is a reversible reaction. The amount of oxyhemoglobin formed depends on the partial pressure of oxygen in the blood. The dependence of the amount of oxyhemoglobin on the partial pressure of oxygen in the blood is called oxyhemoglobin dissociation curve.

The dissociation curve of oxyhemoglobin has an S-shape. The value of the S-shape of the shape of the oxyhemoglobin dissociation curve is the facilitation of the release of O 2 in the tissues. The hypothesis about the reason for the S-shape of the shape of the oxyhemoglobin dissociation curve is that each of the 4 O 2 molecules attached to hemoglobin changes the affinity of the resulting complex for O 2 .

The dissociation curve of oxyhemoglobin shifts to the right (Bohr effect) with an increase in temperature, an increase in the concentration of CO 2 in the blood, and a decrease in pH. The shift of the curve to the right facilitates the return of O 2 in the tissues, the shift of the curve to the left facilitates the binding of O 2 in the lungs.

5.3. Forms of transport of carbon dioxide in the blood

Dissolved in plasma CO 2 (12% CO 2).
Hydrocarbonate ion (77% CO 2). Almost all CO 2 in the blood is hydrated to form carbonic acid, which immediately dissociates to form a proton and a bicarbonate ion. This process can take place both in blood plasma and in erythrocytes. In the erythrocyte, it proceeds 10,000 times faster, since in the erythrocyte there is an enzyme called carbonic anhydrase, which catalyzes the CO 2 hydration reaction.

CO 2 + H 2 0 \u003d H 2 CO 3 \u003d HCO 3 - + H +

Carboxyhemoglobin (11% CO 2) - is formed as a result of the addition of CO 2 to the free amino groups of the hemoglobin protein.

Hb-NH 2 + CO 2 \u003d Hb-NH-COOH \u003d Nb-NH-COO - + H +

An increase in the concentration of CO 2 in the blood leads to an increase in blood pH, since the hydration of CO 2 and its attachment to hemoglobin is accompanied by the formation of H + .

6. REGULATION OF BREATHING

6.1. Innervation of the respiratory muscles

The regulation of the respiratory system is carried out by controlling the frequency of respiratory movements and the depth of respiratory movements (tidal volume).

The inspiratory and expiratory muscles are innervated by motor neurons located in the anterior horns of the spinal cord. The activity of these neurons is controlled by descending influences from the medulla oblongata and cerebral cortex.

6.2. The mechanism of rhythmogenesis of respiratory movements

The neural network is located in the brainstem central respiratory mechanism), consisting of 6 types of neurons:

Inspiratory neurons(early, complete, late, post-) - are activated in the inspiratory phase, the axons of these neurons do not leave the brain stem, forming a neural network.
expiratory neurons- are activated in the exhalation phase, are part of the neural network of the brain stem.
Bulbospinal inspiratory neurons- brainstem neurons that send their axons to the motor neurons of the inspiratory muscles of the spinal cord.

Rhythmic changes in the activity of the neural network - rhythmic changes in the activity of bulbospinal neurons - rhythmic changes in the activity of motoneurons of the spinal cord - rhythmic alternation of contractions and relaxations of the inspiratory muscles - rhythmic alternation of inhalation and exhalation.

6.3. Respiratory system receptors

stretch receptors- located among the smooth muscle elements of the bronchi and bronchioles. Activated when the lungs are stretched. Afferent pathways follow the medulla oblongata as part of the vagus nerve.

Peripheral chemoreceptors form clusters in the area of the carotid sinus (carotid bodies) and the aortic arch (aortic bodies). They are activated with a decrease in O 2 tension (hypoxic stimulus), an increase in CO 2 tension (hypercapnic stimulus) and an increase in H + concentration. Afferent pathways follow the dorsal part of the brain stem as part of the IX pair of cranial nerves.

Central chemoreceptors located on the ventral surface of the brainstem. They are activated with an increase in the concentration of CO 2 and H + in the cerebrospinal fluid.

Respiratory tract receptors - are excited by mechanical irritation with dust particles, etc.

6.4. Basic reflexes of the respiratory system

Inflating the lungs ® inhibition of inspiration. The receptive field of the reflex is the stretch receptors of the lungs.
Decreased [O 2 ], increased [CO 2 ], increased [H + ] in the blood or cerebrospinal fluid ® increase in MOD. The receptive field of the reflex is the stretch receptors of the lungs.
Irritation of the airways ® cough, sneezing. The receptive field of the reflex is the mechanoreceptors of the respiratory tract.

6.5. Influence of the hypothalamus and cortex

In the hypothalamus, sensory information from all body systems is integrated. The descending influences of the hypothalamus modulate the work of the central respiratory mechanism based on the needs of the whole organism.

Corticospinal connections of the cortex provide the possibility of arbitrary control of respiratory movements.

6.6. Diagram of the functional respiratory system

Similar information.

Circulation in the lungs. Blood supply to the lungs. Lung innervation. Vessels and nerves of the lungs.

Arterial blood is brought to the lungs along rr. bronchiales (from the aorta, aa. intercostales posteriores and a. subclavia). They nourish the bronchial wall and lung tissue. From the capillary network, which is formed by the branches of these arteries, vv. bronchiales, partly falling into vv. azygos et hemiazygos, and partly in vv. pulmonales. Thus, the systems of the pulmonary and bronchial veins anastomose with each other.

In the lungs, there are superficial lymphatic vessels, embedded in the deep layer of the pleura, and deep, intrapulmonary. The roots of deep lymphatic vessels are lymphatic capillaries that form networks around the respiratory and terminal bronchioles, in the interacinus and interlobular septa. These networks continue into the plexuses of the lymphatic vessels around the branches of the pulmonary artery, veins and bronchi.

The efferent lymphatic vessels go to the root of the lung and the regional bronchopulmonary and further tracheobronchial and paratracheal lymph nodes lying here, nodi lymphatici bronchopulmonales et tracheobronchiales.

Since the efferent vessels of the tracheobronchial nodes go to the right venous corner, a significant part of the lymph of the left lung, flowing from its lower lobe, enters the right lymphatic duct.

The nerves of the lungs come from the plexus pulmonalis, which is formed by the branches of n. vagus et truncus sympathicus.

The structure of the lungs. Branching of the bronchi. Macro-microscopic structure of the lung.

According to the division of the lungs into lobes, each of the two main bronchi, bronchus principalis, approaching the gates of the lung, begins to divide into lobar bronchi, bronchi lobares. The right upper lobar bronchus, heading towards the center of the upper lobe, passes over the pulmonary artery and is called supraarterial; the remaining lobar bronchi of the right lung and all the lobar bronchi of the left pass under the artery and are called subarterial. The lobar bronchi, entering the substance of the lung, give away a number of smaller, tertiary, bronchi, called segmental, bronchi segmentates, since they ventilate certain areas of the lung - segments. Segmental bronchi, in turn, are divided dichotomously (each into two) into smaller bronchi of the 4th and subsequent orders up to the terminal and respiratory bronchioles (see below).

The skeleton of the bronchi is arranged differently outside and inside the lung, according to different conditions of mechanical action on the walls of the bronchi outside and inside the organ: outside the lung, the skeleton of the bronchi consists of cartilaginous half-rings, and when approaching the gates of the lung, cartilaginous connections appear between the cartilaginous half-rings, as a result of which the structure of their wall becomes lattice.

In the segmental bronchi and their further branchings, the cartilages no longer have the shape of semicircles, but break up into separate plates, the size of which decreases as the caliber of the bronchi decreases; cartilage disappears in terminal bronchioles. The mucous glands also disappear in them, but the ciliated epithelium remains.

The muscle layer consists of circularly located medially from the cartilage of unstriated muscle fibers. At the sites of division of the bronchi, there are special circular muscle bundles that can narrow or completely close the entrance to a particular bronchus.

Macro-microscopic structure of the lung.

Lung segments consist of secondary lobules, lobuli pulmonis secundarii, occupying the periphery of the segment with a layer up to 4 cm thick. The secondary lobule is a pyramidal section of the lung parenchyma up to 1 cm in diameter. It is separated by connective tissue septa from adjacent secondary lobules.

Interlobular connective tissue contains veins and networks of lymphatic capillaries and contributes to the mobility of the lobules during the respiratory movements of the lung. Very often, inhaled coal dust is deposited in it, as a result of which the boundaries of the lobules become clearly visible.

The top of each lobule includes one small (1 mm in diameter) bronchus (average of the 8th order), which still contains cartilage in its walls (lobular bronchus). The number of lobular bronchi in each lung reaches 800. Each lobular bronchus branches inside the lobule by 16-18 more tons of thin (0.3-0.5 mm in diameter) terminal bronchioles, bronchioli terminates, which do not contain cartilage and glands.

All bronchi, starting from the main and ending with the terminal bronchioles, make up a single bronchial tree, which serves to conduct a stream of air during inhalation and exhalation; respiratory gas exchange between air and blood does not occur in them. Terminal bronchioles, branching dichotomously, give rise to several orders of respiratory bronchioles, bronchioli respiratorii, differing in that pulmonary vesicles, or alveoli, alveoli pulmonis, already appear on their walls. Alveolar passages, ductuli alveoldres, ending in blind alveolar sacs, sacculi alveoldres, depart radially from each respiratory bronchiole. The wall of each of them is braided by a dense network of blood capillaries. Gas exchange occurs through the wall of the alveoli.

Respiratory bronchioles, alveolar ducts and alveolar sacs with alveoli form a single alveolar tree, or respiratory parenchyma of the lung. The listed structures, originating from one terminal bronchiole, form its functional and anatomical unit, called acinus, acinus (bunch).

The alveolar ducts and sacs belonging to one respiratory bronchiole of the last order make up the primary lobule, lobulus pulmonis primarius. There are about 16 of them in the acinus.

The number of acini in both lungs reaches 30,000, and alveoli 300 - 350 million. The area of the respiratory surface of the lungs ranges from 35 m2 when exhaling to 100 m2 with a deep breath. From the totality of the acini, lobules are composed, from the lobules - segments, from the segments - lobes, and from the lobes - the whole lung.

Trachea. Topography of the trachea. The structure of the trachea. Cartilages of the trachea.

The trachea, trachea (from the Greek trachus - rough), being a continuation of the larynx, begins at the level of the lower edge of the VI cervical vertebra and ends at the level of the upper edge of the V thoracic vertebra, where it is divided into two bronchi - right and left. The division of the trachea is called the bifurcatio tracheae. The length of the trachea ranges from 9 to 11 cm, the transverse diameter is on average 15 - 18 mm.

Topography of the trachea.

The cervical region is covered at the top by the thyroid gland, behind the trachea is adjacent to the esophagus, and on the sides of it are the common carotid arteries. In addition to the isthmus of the thyroid gland, the trachea is also covered in front by mm. sternohyoideus and sternothyroideus, except in the midline, where the inner edges of these muscles diverge. The space between the posterior surface of these muscles with the fascia covering them and the anterior surface of the trachea, spatium pretracheale, is filled with loose fiber and blood vessels of the thyroid gland (a. thyroidea ima and venous plexus). The thoracic trachea is covered in front by the handle of the sternum, thymus gland, and vessels. The position of the trachea in front of the esophagus is associated with its development from the ventral wall of the foregut.

The structure of the trachea.

The wall of the trachea consists of 16 - 20 incomplete cartilaginous rings, cartilagines tracheales, connected by fibrous ligaments - ligg. annularia; each ring extends only two-thirds of the circumference. The posterior membranous wall of the trachea, paries membranaceus, is flattened and contains bundles of unstriated muscle tissue that run transversely and longitudinally and provide active movements of the trachea during breathing, coughing, etc. The mucous membrane of the larynx and trachea is covered with ciliated epithelium (with the exception of the vocal cords and part of the epiglottis ) and is rich in lymphoid tissue and mucous glands.

Blood supply of the trachea. Innervation of the trachea. Vessels and nerves of the trachea.

Vessels and nerves of the trachea. The trachea receives arteries from the aa. thyroidea inferior, thoracica interna, and also from rami bronchiales aortae thoracicae. The venous outflow is carried out into the venous plexuses surrounding the trachea, and also (and especially) into the veins of the thyroid gland. The lymphatic vessels of the trachea go all the way to two chains of nodes located on its sides (near-tracheal nodes). In addition, from the upper segment they go to the preglottal and upper deep cervical, from the middle - to the last and supraclavicular, from the lower - to the anterior mediastinal nodes.

The nerves of the trachea come from the truncus sympathicus and n. vagus, as well as from the branch of the latter - n. laryngeus inferior.

Lungs. Anatomy of the lung.

The lungs, pulmones (from the Greek - pneumon, hence pneumonia - pneumonia), are located in the chest cavity, cavitas thoracis, on the sides of the heart and large vessels, in pleural sacs separated from each other by the mediastinum, mediastinum, extending from the spinal column behind to the anterior chest wall.

The right lung is larger in volume than the left (approximately 10%), at the same time it is somewhat shorter and wider, firstly, due to the fact that the right dome of the diaphragm is higher than the left one (the effect of the voluminous right lobe of the liver), and, secondly, second, the heart is located more to the left than to the right, thereby reducing the width of the left lung.

Each lung, pulmo, has an irregularly cone-shaped shape, with a base, basis pulmonis, directed downwards, and a rounded tip, apex pulmonis, which stands 3–4 cm above the 1st rib or 2–3 cm above the collarbone in front, but in the back it reaches level VII of the cervical vertebra. At the top of the lungs, a small groove, sulcus subclavius, is noticeable from the pressure of the subclavian artery passing here. There are three surfaces in the lung. The lower one, facies diaphragmatica, is concave according to the convexity of the upper surface of the diaphragm, to which it is adjacent. The extensive costal surface, fades costalis, is convex, corresponding to the concavity of the ribs, which, together with the intercostal muscles lying between them, are part of the wall of the chest cavity. The medial surface, facies medialis, is concave, repeats for the most part the outline of the pericardium and is divided into the anterior part, adjacent to the mediastinum, pars mediastinal, and the posterior, adjacent to the spinal column, pars vertebrdlis. The surfaces are separated by edges: the sharp edge of the base is called the lower, margo inferior; the edge, also sharp, separating the fades medialis and costalis from each other, is margo anterior. On the medial surface, upward and posterior to the recess from the pericardium, there are gates of the lung, hilus pulmonis, through which the bronchi and pulmonary artery (as well as nerves) enter the lung, and two pulmonary veins (and lymphatic vessels) exit, making up the root of the lung. Oh, radix pulmonis. At the root of the lung, the bronchus is located dorsally, the position of the pulmonary artery is not the same on the right and left sides. At the root of the right lung a. pulmonalis is located below the bronchus, on the left side it crosses the bronchus and lies above it. The pulmonary veins on both sides are located at the root of the lung below the pulmonary artery and bronchus. Behind, at the place of transition of the costal and medial surfaces of the lung into each other, a sharp edge is not formed, the rounded part of each lung is placed here in the deepening of the chest cavity on the sides of the spine (sulci pulmonales).

Each lung is divided into lobes, lobi, by means of furrows, fissurae interlobares. One groove, oblique, fissura obllqua, having on both lungs, begins relatively high (6-7 cm below the apex) and then descends obliquely down to the diaphragmatic surface, deeply entering the substance of the lung. It separates the upper lobe from the lower lobe on each lung. In addition to this furrow, the right lung also has a second, horizontal, furrow, fissura horizontalis, passing at the level of the IV rib. It delimits from the upper lobe of the right lung a wedge-shaped area that makes up the middle lobe. Thus, in the right lung there are three lobes: lobi superior, medius et inferior. In the left lung, only two lobes are distinguished: the upper, lobus superior, to which the top of the lung departs, and the lower, lobus inferior, more voluminous than the upper. It includes almost the entire diaphragmatic surface and most of the posterior blunt edge of the lung. On the front edge of the left lung, in its lower part, there is a cardiac notch, incisura cardiaca pulmonis sinistri, where the lung, as if pushed back by the heart, leaves a significant part of the pericardium uncovered. From below, this notch is bounded by a protrusion of the anterior margin, called the uvula, lingula pulmonus sinistri. Lingula and the part of the lung adjacent to it correspond to the middle lobe of the right lung.

It is carried out by two vascular systems:

The pulmonary artery system.

Makes up a small circle of blood circulation. Purpose: saturation of venous blood with oxygen. The pulmonary artery brings venous blood, branches up to the capillaries braiding the alveoli. As a result of gas exchange in the lungs, the blood gives off carbon dioxide, is saturated with oxygen, turns into arterial blood, and exits the lungs through the pulmonary veins.

bronchial artery system.

It is part of the systemic circulation. Purpose: blood supply to the lung tissue.

Bronchial arteries bring arterial blood to the lung, carry out blood supply to the lung tissue (give oxygen and nutrients to cells, take carbon dioxide and metabolic products). As a result, the blood turns into venous blood and exits the lung through the bronchial veins.

Pleura.

The serous membrane of the lung. It is formed by loose connective tissue, covered with a single-layer squamous epithelium with microvilli (mesothelium).

Has two leaves:

- visceral leaf; covers the lung itself, enters the interlobar grooves;

- parietal (parietal) sheet; covers the walls of the chest from the inside (ribs, diaphragm, separates the lung from the organs of the mediastinum.). Above the top of the lung, it forms the dome of the pleura. Thus, a closed pleural sac is formed around each lung.

The pleural cavity is an airtight slit-like space between the two layers of the pleura (between the lungs and the chest wall). It is filled with a small amount of serous fluid to reduce friction between the sheets.

NON-RESPIRATORY LUNG FUNCTIONS

The main non-respiratory functions of the lungs are metabolic (filtration) and pharmacological.

The metabolic function of the lungs consists in retaining and destroying cell conglomerates, fibrin clots, and fatty microemboli from the blood. This is carried out by numerous enzyme systems. Alveolar mast cells secrete chymotrypsin and other proteases, while alveolar macrophages secrete prostheses and lipolytic enzymes. Therefore, emulsified fat and higher fatty acids that enter the venous circulation through the thoracic lymphatic duct, after hydrolysis in the lungs, do not go further than the pulmonary capillaries. Part of the captured lipids and proteins goes to the synthesis of the surfactant.

The pharmacological function of the lungs is the synthesis of biologically active substances.

◊ The lungs are the organ richest in histamine. It is important for the regulation of microcirculation under stress conditions, but turns the lungs into a target organ during allergic reactions, causing bronchospasm, vasoconstriction and increased permeability of the alveolocapillary membranes. Lung tissue in large quantities synthesizes and destroys serotonin, and also inactivates at least 80% of all kinins. The formation of angiotensin II in blood plasma occurs from angiotensin I under the action of an angiotensin-converting enzyme synthesized by the endothelium of the pulmonary capillaries. Macrophages, neutrophils, mast, endothelial, smooth muscle and epithelial cells produce nitric oxide. Its insufficient synthesis in chronic hypoxia is the main link in the pathogenesis of hypertension in the pulmonary circulation and the loss of the ability of pulmonary vessels to vasodilate under the action of endothelium-dependent substances.

◊ Lungs are a source of blood clotting cofactors (thromboplastin, etc.), they contain an activator that converts plasminogen into plasmin. Alveolar mast cells synthesize heparin, which acts as antithromboplastin and antithrombin, inhibits hyaluronidase, has an antihistamine effect, and activates lipoprotein lipase. The lungs synthesize prostacyclin, which inhibits platelet aggregation, and thromboxane A2, which has the opposite effect.

Respiratory diseases are the most common in modern man and have a high mortality rate. Changes in the lungs have a systemic effect on the body. Respiratory hypoxia causes the processes of dystrophy, atrophy and sclerosis in many internal organs. However, the lungs also perform non-respiratory functions (inactivation of angiotensin convertase, adrenaline, norepinephrine, serotonin, histamine, bradykinin, prostaglandins, lipid utilization, generation and inactivation of reactive oxygen species). Lung diseases, as a rule, are the result of a violation of protective mechanisms.

A bit of history.

Inflammation of the lungs is one of the diseases common in all periods of the development of human society. A wealth of material was left to us by ancient scientists. Their views on the pathology of the respiratory organs reflected the prevailing ideas about the unity of nature, the presence of a strong connection between phenomena. One of the founders of ancient medicine, an outstanding Greek physician and naturalist Hippocrates and other ancient healers perceived pneumonia as a dynamic process, a disease of the whole organism and, in particular, considered pleural empyema as the outcome of pneumonia. After Hippocrates, the most important theoretician of ancient medicine was Claudius Galen- Roman physician and naturalist who performed vivisection and introduced the study of the pulse into practice. In the Middle Ages until the Renaissance, Galen was considered the undisputed authority in the field of medicine. After Galen, the doctrine of pneumonia did not move forward for many years. According to the views of Paracelsus, Fernel, Van Helmont, pneumonia was considered a local inflammatory process, and abundant bloodletting was used to treat it at that time. Bloodletting was done persistently, repeatedly, and it is no wonder that the death rate from pneumonia was very high. Until the beginning of the 19th century, no definite anatomical and clinical concept was associated with the name "pneumonia".

In Russia, the history of the study of pneumonia is associated with the name S. P. Botkin. He began to deal with this pathology of a person, undergoing an internship in Germany with R.Virchow; during this period, the formation of the cell theory took place, and dogmas were discussed Rokitansky.

Observing patients in the clinics of St. Petersburg, in the weekly Clinical Newspaper, S. P. Botkin described severe forms of pneumonia in six lectures, which were included in the Russian-language literature under the name lobar pneumonia. A well-known doctor, introducing the term croupous pneumonia, had in mind a severe respiratory disorder, reminiscent of croup in its clinical manifestations. Croupous pneumonia was one of the most severe diseases, deaths exceeded 80%.